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Topic: EM Drive Developments Thread 1 (Read 1019097 times)

Conceptually, it's the same as a book lying on a desk. Desk is exerting a force on the book to counteract gravity but no energy is expended. Energy is force times distance. If a force is exerted on an object but the object doesn't move, no energy need be expended.

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Chris Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

well if the ME idea turns out to be valid there might be an Ansible in it for free.

of course accepting the ME idea there are several proposed mechanisms by which it could work. but if the ME is valid and it turns out to involve Freeman's advanced and retarded wave explanation then because inertia would be a result of communication with distal parts of the universe then you should be able to modulate an ME device output and send encoded information.

I am not sure that's a very good idea to send out info to who knows what & where.

I have a general magnetism question that this thread has made pop into my mind. How can magnets attract or repel each other indefinitely without expending energy? If I put two ring magnets on a pole with the same pole facing each other, the magnet on the top will float above the magnet on the bottom, the repulsive force overcoming gravity, and the equilibrium distance between the two is determined by the field strength of the magnets. All that is well and good, but how does this happen without the repulsive (or attractive) effect fading over time and the magnets getting warm or otherwise emitting photons? In other words, the floating magnet is continually resisting an accelerative force due to gravity, so it (and the other magnet) has to expend energy to counter gravity for it to stay afloat. So where does that continual input energy come from? Even if it's at the nuclear level, there has to be an expenditure somewhere in order to negate gravitational acceleration.

Actually, I think all the Aliens out there are mad at us for not trying to contact them sooner... Kind of like when you don't call your family for a while and they give you the cold shoulder...

Conceptually, it's the same as a book lying on a desk. Desk is exerting a force on the book to counteract gravity but no energy is expended. Energy is force times distance. If a force is exerted on an object but the object doesn't move, no energy need be expended.

Thanks for responding!

How can a force be exerted without expending energy? (serious question). If I hold my fat aunt above my head and she doesn't move, I'm still using energy to exert a force to counter gravity. Aren't atoms and particles doing the same? Inversely, can't I also expend energy to squeeze them together until the atoms can no longer resist fusing and then lots of their energy is released. Is the energy expended still zero until the whole thing collapses?

As Robotbeat states, no energy need be expended, that don't mean any "agency" that holds a force (on an object that doesn't move relative to the agent exerting said force) wont dissipate energy : muscles do use metabolic energy even when they are not doing useful work, as is the case when contracting without displacement. The same would apply for a DC electric motor exerting a torque on a stuck shaft, no displacement implies no useful work, yet the motor is dissipating energy. In both cases the whole energy used by the agent is completely converted to heat, while if displacement is done in the same direction as force then at least a fraction of the expended energy goes into useful work, like for instance gaining height (more gravitational potential energy for the pushed object) or speed (more kinetic energy). Said useful work's corresponding energy can be recovered later, that is converted to other forms...

A solid "passive" object like a chair can hold a force on an object without expending any energy but it cant follow displacement in the direction of force, if aunty is an inch above chair then chair is no longer exerting force on aunty : no energy needed to exert force but no useful work can be done. In general : useful work is less or equal to expended energy. No expended energy implies no useful work, useful work implies expended energy, but it's possible to expend energy without useful work (in which case efficiency is 0, and expended energy is dissipated as heat).

Like with a chair, you could keep two nucleus (say two deuterium) at a close distance by applying a static force opposite to the electrostatic repulsion, without expending any energy, but the electrostatic repulsion wouldn't get tired because it's not expending energy either. On the other hand to take two nucleus from the "long" distance you find them and get them to the closer distance you wish, your squeezing force has to exert through a displacement : that needs expending energy. More energy can be recovered when the two nucleus fuse together (strong nuclear force bigger than electrostatic repulsion at close ranges) but that's another story, you have to invest initial energy to get (not to keep) nucleus close first.

Now the confusing thing at microscopic scale is that there is no such thing as a solid object. Solidity is a consequence of chemical bonds : electromagnetic forces mediated by constant exchanges of photons. That don't sound really static and yet no net expenditure of energy is needed when no displacement is done overall. Even if talking about inflatable chair and all gas atoms keep moving around, they support aunty "for free" as far as energy is concerned, they don't get tired.

So coercivity seems to imply that there is a fixed amount of time that it will levitate the other magnet, and whatever is actually responsible for the levitation will dissipate as heat over time. Right? No magic involved, something is being spent.

Chris Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

So coercivity seems to imply that there is a fixed amount of time that it will levitate the other magnet, and whatever is actually responsible for the levitation will dissipate as heat over time. Right? No magic involved, something is being spent.

Again : theory (classical or quantum mechanics) states that it is not necessary to spend energy to hold a force in a geometrically static (no displacement) system, even when the force is at distance (and at microscopic scale even a solid contact is in fact force at distance). Not necessary don't mean that any way to achieve such force won't show some level of power loss or wear or creep deformation or weakening. A block of iron supporting an object of one pound will exert a force (against the weight of object) and maintain its altitude forever without spending anything : no magic involved, force without displacement needs no net energy expenditure. Force is not energy. The "forever" is true on cosmological scales, at least a few billion years, after what dark energy could maybe start to rip space-time apart at mundane scales. Resting without spending energy, quite literally until the end of time : no magic involved.

There is no theoretical reasons (basic principles) why a magnetically "levitating" object would require more energy that an object resting on a solid block, actually the object is also "levitating" in the later case, only a few angstroms above the support. See "contact force" on wikipedia :

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The interaction between macroscopic objects can be roughly described as resulting from the electromagnetic interactions between protons and electrons of the atomic constituents of these objects. Everyday objects do not actually touch each other; rather, contact forces are the result of the interactions of the electrons at or near the surfaces of the objects (exchange force).

So there is nothing much special between just resting on a solid object (no energy needed, forever) and resting on a magnetic repulsion from a permanent magnet at longer distance : theoretically no energy needed. If you keep the fields well below coercivity limits and use appropriate materials this is also possible in practice. Demagnetization occurs mainly not as a function of time but of external magnetic field strength, that is below a certain level of external field the demagnetization time approaches infinity.http://www.magmamagnets.com/permanent-magnet-stability

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The effect of time on modern permanent magnets is minimal. .../... Over 100,000 hours, these losses are in the range of essentially zero for Samarium Cobalt materials...

Also for a very very long functioning, some environmental radiation can wear the magnets :

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SmCo exhibits significant demagnetization when irradiated with a proton beam of 10^9 to 10^10 rads

. I guess cumulative radiations would also discharge the current loops in a superconductor...

So, granted the opposite magnets levitation is more difficult to achieve and "fragile" than the levitation of just resting on a solid support but in both cases spent energy is 0, without magic involved. Of course if you used (not superconducting) electromagnets instead of permanent magnets then maintaining the force would need constant energy flow (power), but not out of basic principles fatality, just as a consequence of a technological choice. It's always possible to use more energy than needed.

My interpretation of the Nasa description of the test campaigns tells me that the shape of the thruster and the q factor make no difference. The presence of the dielectric and the electromagnetic flux are key. If it really works, it's due to photon momentum transfer described by Minkowski et al. Also describing quantum vacuum particle pair production / annihilation as a plasma is gobbledygook. The quantum vacuum is key here though, as it is the only way I can think of to bring about an asymmetry which would allow thrust to occur, and not have a violation of laws of thermodynamics. Just as the qv is responsible for the lamb shift observed in a shift in the energy levels of hydrogen atom atoms, I think the thruster may work in a similar but reverse way. A net thrust cannot occur via photon momentum transfer within the same frame of reference, but it could if energy could be transferred to another frame of reference. No violation of laws, net thrust. If this works, it could be describing a key asymmetry which could point to new physics. There are a lot of papers describing mechanisms similar to this, check out works by Feigel, Dewar, Millis (Nasa), Brito. I think this thruster would work best if it were just a tube with a dielectric slug of PVDF instead of PTFE, pumped with a huge amount of wideband RF white noise.

Since the emdrive isn't expelling anything, there isn't anything in our frame of reference to allow a symmetrical reaction to occur, like a rocket blast creating an equal and opposite reaction, giving you thrust. If it were expelling something, like the radiation it is producing, it would merely be a photon thruster. But it isn't expelling anything, so imagine a rocket with the cone capped off, no reaction. This is where the dielectric comes in, it is providing a vector through to another frame of reference, that of the qv (composed of the ground states of all particles, all fields, all frequencies, which luckily fluctuates according to the uncertainty principle) and most importantly, another frame of reference. There the photons can interact and transfer some of their energy/momentum only fleetingly and achieve thrust. Fleetingly in that there is a very low probability of any interaction whatsoever. The dielectric serves to up a photons chances of interacting with the qv, nothing more. Some geometries and materials allow for repulsive Casimir effects. Just shooting RF out the back of the thruster will interact with something once in a very long while and give you a tiny bit of thrust. It looks like the dielectric ups those chances of an interaction some 16000 times. In the end everything is conserved, the energy is transferred to another frame of reference, reacts, and thrust occurs against the very weakly interacting qv. This isn't a reactionless thruster. So to improve the design, we need to improve our chances of interacting with the qv, which has a very low probability wave function, hence a low probability of ever being interacted with. Advanced materials, like PVDF (love this stuff), coupled with a very high power rf field at a frequency where the dielectric constant of the material is highest (permittivity peaks and dips at different frequencies), taking into account that the higher the frequency, the higher the photon energy. So using the highest frequency possible where the dielectric constant is highest, coupled with noisy high rf wideband power should be the ticket. #IFLScience

it could if energy could be transferred to another frame of reference. No violation of laws, net thrust.

Frames of reference aren't physical entities. You can't transfer energy or momentum or anything from one frame of reference to another.

Frames of reference are just different ways of observing exactly the same physical events. Think of them as places observers could be to watch. Relativity tells us that exactly the same rules are followed in all inertial frames of reference.

Talking about transferring energy to another frame of reference doesn't make any more sense than saying I can accelerate by pushing against my own shadow. It's like saying I'm going to work on extracting energy from the number 3.

Chris Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

The mean local velocity (or momentum) vector of a relatively homogeneous flow of real particles (known or unknown) can define a local frame of reference, and you can conceivably transfer momentum from a device to such a flow, would that phrase be more accurate ? Known flows include solar wind, photon flows near hot objects, photon flow of the CMB, photons mediating planetary magnetic fields, wind (in atmospheres)... Undetected but suspected flow would include dark matter, cosmic neutrino background, gravitational waves . Other possible unknown fields are well, unknown. Obviously inside the walls of a vacuum chamber in an earth lab a number of those flows are ruled out.

Virtual particles of the vacuum on the other hand don't appear to define a frame of reference, though they might define an "inertial reference" (tm) : Casimir effect for instance don't show different behaviour on different inertial frames (Lorentz invariant, no reference of what would be an absolute 0 speed relative to vacuum) while dynamical Casimir effect allows to measure acceleration in absolute terms (can tell an absolute 0 acceleration relative to it). Don't know when gravity comes into play but in a flat space-time it seems hard to push on such a "medium" without breaking conservation of energy because of acquiring a reaction mass always at 0 speed relative to it (cost don't depend on a varying relative speed as would be the case with a real flow). So if energy is gained it would imply either to abandon conservation (and time invariance) or to tap into vacuum zero-point energy, which would no longer be zero-point... My guess is that all this virtual agitation down there is like a thermal bath and nothing useful (in terms of net work) can come out of it (second principle...) but please someone qualified help. If no useful work can be taped, then no cheap momentum exchange can be taped. The only help of virtual particles is when they come real but that needs same amount of energy/mass you would have to throw backward anyway to get momentum forward in classical reaction propulsion.

I'd like to see some qualified explanations with Feynman diagrams showing how it's impossible to push on virtual particles (unless they are made real at equivalent energy/mass cost).

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It's like saying I'm going to work on extracting energy from the number 3.

You could still extract energy from the work of trying, couldn't you ?

The CMB is a certain reference frame (just like another reference frame), but why the crap should you be able to push against it or whatever you're talking about? There is no "ether."

frobnfiahdfh:The virtual particles work the same in every reference frame. And you COULD "push" on them, if you wanted to expend the necessary energy to make them real particles, but that'd be no more efficient than a photon drive.

Chris Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Conceptually, it's the same as a book lying on a desk. Desk is exerting a force on the book to counteract gravity but no energy is expended. Energy is force times distance. If a force is exerted on an object but the object doesn't move, no energy need be expended.

Thanks for responding!

How can a force be exerted without expending energy? (serious question). If I hold my fat aunt above my head and she doesn't move, I'm still using energy to exert a force to counter gravity. ...

...A solid "passive" object like a chair can hold a force on an object without expending any energy but it cant follow displacement in the direction of force, if aunty is an inch above chair then chair is no longer exerting force on aunty

If you pardon me the explanation of "energy equal force multiplied by distance and there is no distance involved", in my opinion of a layman is not enough to answer to "how a force can be exerted without expending energy". Actually it seems to me more a tautology than an explanation.- It assumes an empty universe where two elements are considered in a static way. Using the concept of force is meaningless in this situation as they do not move, and by definition no energy is involved so IMO there is no explanation given. The key answer lies in energy budget in several states, including potential energy in its magnetic and gravitation aspects. Work is one form of energy, but there are many other forms, ultimately energy is a scalar, a quantity without direction attached contrary to a force which as a vector has a direction, and it is linked to the notion of mass. The energy concept is usefull to describe situations like the one proposed by sghill, as because by definition it is conserved from one state to the next, it easy to trace how it is transfered from one element to the other. - If on earth we have a book at rest on a desk, it has more energy than the same book on the floor i.e. if it falls its energy could be transfered to another device. The desk do not fall because the manufacturer did put energy in it, and if you go as far as that, by assembling atoms, atoms can store energy at different places. When the book is put upon the desk, the desk and the book atoms store the gravitational potential energy of the book. If you remove the desk, the book last potential energy gain will be released and the book will fall to the next lower energy level (on the ground).- It's the same for the two magnets of sghill, one is above the other, so this one has more potential energy, where does it comes? As the first magnet was put above the other, it gained in potential energy from the hand of the person who did it.It can only goes down by sghill design and the other magnet pushes back on it, so where is the potential energy stored? It is in the atoms magnetic field. This is not free energy because energy had been initially used to magnetized those magnets, and the magnets do not permanently loose or gain energy when they are close to each other, because the previous energy budget will be restored as they will be pulled apart.

The CMB is a certain reference frame (just like another reference frame), but why the crap should you be able to push against it or whatever you're talking about? There is no "ether."

CMB photons do carry momentum so it might be possible to either sail relative to them or push on them but it's so weak I guess it's irrelevant for practical propulsion, better just make the photons onboard.

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Energy density of CMB is ~1eV/cm-3, comparable to that of starlight in the Milky Way.

frobnfiahdfh:The virtual particles work the same in every reference frame. And you COULD "push" on them, if you wanted to expend the necessary energy to make them real particles, but that'd be no more efficient than a photon drive.

Completely agree, unless whole contemporary physics turned on its head. Precisely what I meant was "work the same in every inertial reference frame".frobnfiahdfh ?

JPLeRouzic :I can't find simple ideas to explain why energy = force x distance, all other ways to define energy relative to force would fail empirically so we could only relate that to convincing experiments and sensible definitions, or we could be deriving this "rule" from more basic principles (microscopically there is no "force", only momentum exchanges between bosons and fermions) that themselves would have to be admitted or understood from less mundane experiments...

My example of a passive object with a supporting force that don't "follow displacement" wanted to avoid the potential energy complexities involved with springs and possible oscillations around an equilibrium, maintaining the macroscopic equilibrium point by itself needing no net energy spending while quite a lot of energy can be buzzing around. Microscopic thermal agitation is a perpetual motion after all, the bottom of energy, where useful energy is "lost" as heat. Apart from the strange musings about "2 elements considered a static way in empty universe" I don't understand, the rest of what you say makes perfect sense and seems correct to me.

But how does this "force with no net spent energy" point relates to the topic ? A thruster has to exert a force through displacement (in any inertial frame since you also want to accelerate) so the distance term can't be 0 and spent energy can't be 0 either.

The CMB is a physical entity. There is a reference frame associated with it. That doesn't make the reference frame a physical entity.

There is also a reference frame associated with the Earth. It's just the frame in which the Earth is at rest. That doesn't make the reference frame a physical entity you can transfer energy to or from. You can transfer energy to and from the Earth. You cannot transfer energy to and from the Earth's reference frame.

Again, it's like confusing the number 3 with a physical object. It's like saying I'm going to construct three spaceships that have a shared drive that transfers momentum to the number 3 and thus produces thrust. The fact that the number three is associated with something physical (three spaceships) doesn't make the number three a physical object, even though there are physically three spaceships.

You're really not helping your case for the plausibility of the EmDrive by displaying a profound misunderstanding of the most basic concepts of high school physics.

If you pardon me the explanation of "energy equal force multiplied by distance and there is no distance involved", in my opinion of a layman is not enough to answer to "how a force can be exerted without expending energy". Actually it seems to me more a tautology than an explanation.

It's not a tautology or an explanation. It's a definition. It's the definition of the term "work" in physics.

It turns out that if we define work that way, it's a useful concept for predicting what will happen in the physical world. It turns out that if you look at the work done combined with some other quantities, the sum never changes. This is called conservation of energy. Work is just one component of energy, really.

It seems strange that a force that isn't moving an object expends no energy only because it conflicts with many of our every-day experiences. For example, if we push hard against a wall, we apply force to it, and there is no movement, but it tires us out to keep pushing. So we think that we have to use up energy to keep a force applied even when there is no movement.

But we're fooled in this case, because work is being done, we're just not seeing it. That energy is turning into heat, which is just movement of molecules.

So, when we try to apply a force directly with our muscles, we have to expend energy even if there is no obvious movement because we are causing lots of molecules to move around more quickly.

On the other hand, a magnet is a good example of an everyday object that can keep applying a force with no energy expended. Put a magnet on your refrigerator and it will stay there for years. It will keep applying a force to stick the magnet to the refrigerator, but no energy will be expended.

The magnet is capable of applying a force continuously without expending energy. The magnet doesn't leak energy by causing something to heat up. Your muscles are not capable of that.